In the iron and steel industry, metallurgical dusts are produced in numerous metallurgical processes. Thus, in the manufacture of steel using known L.D.-processes, the corresponding converter steel dust is produced and is collected via suitable filtering plants. The dust has a very high metal content, iron being present in predominantly metallic or oxidic form, depending, in each case, on the method used.
The dumping of such dusts constitutes an increasingly difficult environmental and cost problem. Its high metal content argues in favour of a reutilization of the dust, and there was, therefore, also no shortage in attempts to return this dust into the steel manufacturing process.
Dusts having a high content of metallic iron and, above all, portions of pyrophoric iron, are briquetted using hot briquetting processes and are returned to the converter. Also known are the methods of direct feeding of dust into the converter and granulation processes, with the addition of binding agents. In the case of these last-mentioned methods, substances which are not very favourable for the metallurgical process, are, however, also introduced into the converter. Thus, U.S. Pat. No. 833 630 describes a process for the briquetting of brittle ores, wherein the use of a special limestone mixed with magnesium oxide and Portland cement is regarded as being essential since, otherwise, an adequate strength of the ore briquette is not obtained. The water content of 18 to 20% contained in the ore is of decisive importance for the hydraulic reaction with the Portland-cement binding agent. In this known briquetting process, the desired strength of the ore briquette is obtained solely through the reaction of the Portland cement.
A similar process is described in DE-B 1 142 442. The subject matter of this publication is a process for the briquetting of refined ores. The basic additive, in particular magnesium hydrate and/or calcium hydrate, used for the briquetting of the refined ores, constitutes a binding agent which reacts with the carbon dioxide from the air to form a carbonate and, in this way, ensures the desired strength of the ore briquette.
Metallurgical dusts which require disposal or, if possible, recycling are also produced in other metallurgical processes, such as in the manufacture of electrosteel or in the aluminium industry.
It is now the object of the present invention to provide a new process for the cold briquetting of metallurgical dusts which will overcome the disadvantages of previously known processes and which permits an advantageous reutilization of, for example, converter steel dust in the converter.